Why does calling `.index` on a list after using `.reverse()` method result in an `AttributeError`?

Reversing a List with Chainable Methods

In the code snippet you provided, you're attempting to reverse a list using the .reverse() method and then immediately chain another method (.index) on the reversed list. However, .reverse() modifies the list in-place and returns None, which is why you receive the error AttributeError: 'NoneType' object has no attribute 'index'.

To avoid this issue, you can use slicing to return a reversed copy of the list. Slicing with [::-1] reverses the order of the elements in the list and creates a new list without modifying the original one:

formation[::-1]

This expression returns a reversed copy of the formation list, which you can then use to call .index on:

def solution(formation):
    return (formation.index(bCamel) > (len(formation) - 1 - (formation[::-1]).index(fCamel)))

With this modification, the solution function will successfully determine whether the index of 'B' (bCamel) in the formation list is greater than the index of 'F' (fCamel) in the reversed formation list, minus the length of the formation list. This is essentially a check to see if 'B' comes before 'F' in the reversed formation.

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